Apparatus for pneumatically placing semi-fluid materials

ABSTRACT

Quick-setting concrete is applied to a work surface by air conveying wet concrete through a hose to a nozzle and air conveying a dry accelerator powder for the wet concrete through a separate hose into juncture with the stream of suspended wet concrete a predetermined distance back of the nozzle. A positive metering concrete pump meters the concrete into a T-intersection where compressed air entering through one side of the top of the T impinges at substantially right angles to the flow of wet concrete through the base of the T resulting in shearing off of discrete pieces of wet concrete which are conveyed through a hose attached to the other side of the T-intersection. The positive metering concrete pump is directly attached to a positive metering device for the accelerator powder so as to maintain the ratio of wet concrete to accelerator constant.

[ Aug. 28, 1973 1 APPARATUS FOR PNEUMATICALLY PLACING SEMI-FLUIDMATERIALS [76] Inventor: John T. Broadfoot, 12714 Aurora Ave. North,Seattle, Wash. 98133 22 Filed: Aug. 27, 1971 211 App]. No.: 175,764

Related U.S. Application Data [63] Continuation of Ser. No. 175,764,June 18, 1970,

2,788,953 4/1957 Schneider 222/134 X 3,067,987 12/1962 Ballon et a1222/145 X 3,176,878 4/1965 Hobgood et al. 222/134 3,385,476 5/1968 Young222/134 Primary Examiner-Lloyd L. King Attorney-Seed, Berry & Dowrey [57] ABSTRACT Quick-setting concrete is applied to a work surface by airconveying wet concrete through a hose to a nozzle and air conveying adry accelerator powder for the wet concrete through a separate hose intojuncture with the stream of suspended wet concrete a predetermineddistance back of the nozzle. A positive metering concrete pump metersthe concrete into a T-intersection where compressed air entering throughone side of the top of the T impinges at substantially right angles tothe flow of wet concrete through the base of the T resulting in shearingoff of discrete pieces of wet concrete which are conveyed through a hoseattached to the other side of the T-intersection. The positive meteringconcrete pump is directly attached to a positive metering device for theaccelerator powder so as to maintain the ratio of wet concrete toaccelerator constant.

7 Claims, 4 Drawing Figures Patented Aug. 28, 1973 3,754,683

2 Sheets-Sheet 1 JOHN T. BROADFOOT INVENTQR.

BY @M ATTORNEYS Patented Aug. 28, 1973 2 Sheets-Sheet 2 m 8 7 Q. 3 35 4344 /37 l (W HG=2 1 1F1IG== 3 JOHN T- BROA DFOOT INVENTOR.

BY I Q ATTORNEYS APPARATUS FOR PNEUMATICALLY PLACING SEMI-FLUIDMATERIALS CROSS-REFERENCE TO RELATED APPLICATIONS This application is acontinuation of Application Serial No. 175764, filed June 18, 1970,entitled APPA- RATUS AND METHOD FOR PNEUMATICALLY PLACING SEMI-FLUIDMATERIALS, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to an apparatus and method for metering, conveying and applyingwet concrete or other semi-fluid materials to a work surface, thesemifluid material having a quick-setting additive or accelerator addedthereto just prior to application to the work area.

2. Prior Art Relating to the Disclosure Quick-setting additives forconcrete which provide an initial setting of the concrete in a matter ofseconds have, of recent, become available. These additives have beenadded in dry form to a dry concrete mix which is then applied to a workarea by means of a nozzle through which water in controlled amounts isdirected. Such a process is very useful in providing ground support inmines and tunnels, thereby replacing the conventional timber and steelsupports, and in repairing concrete structures, sewer lines, buildingretaining walls, water lines, etc.

Two basic methods of pneumatically placing concrete have been used, thedry method and the wet method. By the dry method, measured amounts ofcement, sand and aggregate are mixed dry and forced by compressed airthrough a hose to a nozzle where water is introduced into the drymixture before ejection from the nozzle. Theprincipal disadvantage ofthe dry method is the lack of adequate control of the amount of wateradded to the dry mixture. The amount of water used is critical toobtaining optimum concrete. The amount of water is controlled generallyby the nozzle operator during application. His judgement, or the lack ofit, is the criteria used and the results generally obtained are lessthan optimum. In addition to this disadvantage the dry process requiresthat the sand used be pre-dried, thus limiting use of the process toperiods of good weather.

The so-called wet method utilizes a mixture of measured water andweighed amounts of cement, sand and aggregate. By adding a measuredamount of water to the dry mix before application the quality anduniformity of the concrete can be closely controlled. Rebound, definedas the amount of material sloughing off the surfaceapplied duringapplication, is reduced. One of the main problems encountered in the wetmethod is finding a way of transferring the wet concrete mixture fromthe mixing station through a'hose or other conduit to the nozzle. Whenapplying concrete pneumatically it is desirable to use concrete mixeshaving a minimum of water (a stiff consistency) in order to promotequicker setting and reduced rebound. Such mixes are very difficult toconvey through a hose because of their frictional resistance to passagethrough a hose. Machines for pneumatically placing wet concrete areknown, such as the True Gun-All machine manufactured by the Detroit ToolEngineering Company of Lebanon, Missouri. This machine is incapable ofsmooth delivery of material and requires a high degree of maintenance.The amount of rebound is greatly affected by the flow of the material.When the flow of the material is uneven the rebound is significantlygreater. Additionally, when a quick-setting additive or accelerator isadded to the concrete mix before ejection from the nozzle using one ofthe True Gun-All machines it is impossible to get uniform distributionof the accelerator due to the erratic flow of wet concrete. The TrueGun-All machines utilizes a cylindrical air pressurized mixing drum inwhich multiple paddle wheels rotate, each of the paddles having wipingblades thereon which contact the inner surface of the drum. Alternateslugs or measured amounts of wet concrete and compressed air from asource other than the interior of the tank are produced, the compressedair forcing the slugs of concrete through a hose to a nozzle.

Another means of conveying and spraying wet cementitious materials isdisclosed in U.S. Pat. No. 3,212,759 which utilizes a pressurized tankholding the concrete, the tank having therein aereating means foruniformly dispersing high pressure air in the form of small bubbleswithin the mass of cementitious material to decrease its internalfriction and facilitate delivery through a hose or a conduit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of theoverall apparatus of this invention which includes a positive meteringfluid pump, a metering device for an accelerator powder for the pumpedfluid, means connecting the fluid pump and the metering device directlytogether, and conduit means for deliveringthe mixed fluid andaccelerator out of a common nozzle;

FIG. 2 is a cross-sectional view along section line 2-2 of FIG. 1;

FIG. 3 is a partial cross-sectional view along section line 3-3 of FIG.2 illustrating the agitation means within the holding vessel for theaccelerator; and

FIG. 4 is a cross'sectional view of the T-section into which the fluidis metered by the fluid pump and in which compressed air is impingedagainst the fluid at substantially right angles thereto.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1,the overall apparatus of this invention comprises a frame or basesupport I on which is mounted a fluid pump 10, a supply hopper for thepump 20, and a metering means for an accelerator powder 30.

Fluid pumps capable of efficiently handling fluids of heavy consistencyin which solids are entrained and which deliver a relatively smooth flowof the fluid are the type used in this invention. The pump is preferablyof the type whereinthe fluid to be pumped is com-. pletely isolated fromthe moving parts of the pump. A preferred type of pump for the heavyfluids used in this invention, particularly concrete in which rock oraggregate up to one inch in diameter is included, is described in US.Pat. No. 3,180,272 which is hereby incorporated by reference. Asdescribed, fluid pumps of this type comprise a housing 11 comprised of acylindrical shell with headers bolted thereto as closures for the openends thereof. Each of the headers have a centrally located aperture toaccommodate a rotary shaft. Air seals surround the shaft within theapparatus in the outer end walls. Entry and exit ports are provided inthe cylindrical housing for a deformable or flexible hose to be receivedtherethrough, the hose extending about and bearing against the interiorsurface of the cylindrical housing. One of the ports serves as the entryport for the material to be pumped with the other port serving as theexit port. Only the exit port 12 is shown in FIG. 1. Within the housingand mounted on the shaft is a power driven rotor means which squeezesthe hose section within the cylindrical ring in repeating cyclesstarting at the entry end and working progressively towards the exitend. While the particular pump shown in the patent mentioned aboveutilizes two opposed elastic tires mounted for orbital travel around thecenter of the cylindrical housing, other rotor designs may be employed.If desired, only one elastic tire centrally mounted around the shaft maybe used, or four elastic tires arranged at right angles to each other inpairs using the planetary arrangement shown in the patent may be used.

Pumps of the type shown in the above mentioned patent are capable ofefficiently pumping heavy fluids containing aggregate ranging in size upto one inch in diameter. The shaft of the pump is connected to asuitable power means (not shown). In FIG. 1, a shield is shown shieldingthe belt driving the shaft of the concrete pump for safety reasons.

In front of the fluid pump and mounted on the same base support is afeed trough 20 in which cement and sand or cement, sand and aggregateare mixed prior to being pumped. The entry port of the pump communicateswith the trough 20. The feed trough 20 includes several rotor blades 21mounted on a shaft 22 running through the trough, the shaft being drivenby suitable power means (not shown). The rotor blades 21 thoroughly mixpredetermined amounts of wet concrete made up of water, sand and cement,or water, sand, ce ment and aggregate.

Directly connected to the fluid pump is a metering device 30 formetering predetermined amounts of a dry accelerator powder into theconduit for the wet concrete for quick setting thereof. The meteringdevice comprises a cylindrical holding vessel 31 for the acceleratorpowder supported on a base support 32 by legs 33. The holding vessel hasa bottom wall which tapers to an opening of smaller diameter than thecylindrical holding vessel. The opening in the bottom of the holdingvessel communicates with an opening in the side wall of conduit 34running horizontally to the vertically disposed holding vessel. Withinconduit 34 is mounted a feed screw 35 rigidly attached to shaft 36 onwhich is mounted a variable speed pulley 37. Around the pulley istrained a belt 38 which is connected to the power means powering thefluid pump. A second pulley 39 around which belt 40 is trained, runs anagitator assembly to be described.'The agitator assembly is shown incross-section in FIG. 2 and comprises a shaft 41 extending horizontallyand transversely through the holding vessel 31. The shaft has two ormore eccentric portions 42 on which are mounted section of chains 43which, as shaft 40 is rotated, move vertically upwardly and downwardlyto agitate the dry accelerator powder in the vessel. Also mounted onshaft 41 are one or more blades 44 which aid in maintaining theaccelerator powder in a free flowing state. The holding vessel 31 isconstructed so that it can be pressurized. The top of the holding vesselis fitted with a funnel 45 which aids in filling the vessel with theaccelerator powder. The vessel is sealed with a domed closure 45 whichseals around the top opening. The closure 46 is opened and closed byshaft 47. A small diameter valved conduit 48 communicating with theinterior of the vessel 31 is provided to bleed off pressure in vessel 31when refilling is necessary. The accelerator powder should besubstantially free of moisture to achieve optimum results.

A conduit 50 is secured to the exit port of the concrete pump andextends to a T-section 51. The T- section 51 comprises a base portion 52secrued to the discharge opening of the conduit 50 through which fluidis to be pumped and a top section 53 through one end of which compressedair is fed through conduit 54.

Semi-fluids of stiff consistency, such as a so-called dry concretemixture, (one which has a minimum of water added thereto), are verydifficult to pump any distance because of the high friction ofresistance of the material against the internal walls of the hose orconduit through which they are pumped. It is a decided advantage of thisinvention that wet concrete of heavy consistency, that is wet concretehaving a minimum of water therein, can be pumped distances greater than200 feet without difficulty. This is accomplished by metering the wetconcrete sections of the concrete with compressed air entering the topof the T-section through conduit 54. The compressed air impinges on thewet concrete being extruded into the T-section by the fluid pump andcarries it through conduit 55 to nozzle from whic it is sprayed onto awork surface. The pressure of the compressed air needed to force theconcrete through the conduit 55 can be regulated as desired. Thedischarge end of conduit 50 has an internal diameter about three inchesas shown in FIG. 1 and the base of the T-section has an internaldiameter of aboutthe same. The conduit 55 leading from the T-section ofthe nozzle shown in FIG. 1 has an internal diameter of about 2 inches.Though the diameter is reduced from 3 inches to 2 inches there has beenno difficulty in conveying the concrete for distances over 200 feet andup to 300 feet. Compressed air at about 60 psi has been used althoughthis can be varied as desired. Because the air stream is moving theconcrete through the 2 inch line, the fluid pump becomes a meteringmachine having a maximum back pressure of about psi. The fluid pumpdelivers the wet concrete into the T-section in short sticks of materialper rotor turn. The compressed air, however, exerts an elongating effecton the wet concrete resulting in a smooth metered feed at the nozzle.

The accelerator powder is introduced into the wet concrete throughconduit 56 which intersects conduit 55 at an angle a predeterminteddistance back of nozzle 60. The accelerator powder is fed into conduit56 by feed screw'35 and is air suspended by compressed air comingthrough conduit 56 at substantially right angles to the feed of theaccelerator powder. The air suspended accelerator powder mixes with thewet concrete coming through conduit 55 at the intersection of conduits55 and 56. The point of mixing of the accelerator and wet concretedepends upon the kind and amount of accelerator used, the consistency ofthe concrete and other factors. The distance may be from 3 to 10 feetback of the nozzle and preferably a distance of about 6 feet.

The amount of accelerator powder delivered into juncture with the wetconcrete is directly and accurately controlled by directly connectingthe metering device for the accelerator powder to the fluid pump.Preferably an amount of accelerator powder ranging from 2 to 8 percentby weight of the cement content of the concrete is used. The variablebelt speed control connected to pulley 37 enables varying amounts ofaccelerator powder to be mixed with the wet concrete prior to expulsionof the concrete from the nozzle. The optimum amount of acceleratorneeded for a particular application can be ascertained by one skilled inthe art. There are a number of accelerator powders for wet concretecommercially available and any of these may be used.

The overall system comprises a positive metering concrete pump to whichis directly powered a positive metering dry accelerator feed. Theconcrete is conveyed by air through a hose and the powered acceleratoris conveyed by air through a separate hose into juncture with theconcrete hose a predetermined distance before issuing from the nozzle,preferably around 6 feet. The positive metering of the wet concrete intothe air stream gives a very smooth feed at the nozzle and gooddistribution of the accelerator within the concrete mixture.

Utilizing the apparatus shown in FIG. 1, concrete containing aggregateup to one inch in diameter has been conveyed up to 200 feet withmaintenance of good volume feed. A sand-cement mix has been conveyedover 300 feet. The concrete mixers which have been conveyed with theapparatus of this invention have consisted of about 40 percent rock oraggregate and 60 percent building sand, the aggregate having an averagesize of about 7/8 inch in diameter. Rebound is very much reduced withthe apparatus of this invention over that accomplished by the prior art.Application rates are higher than machines of the prior art, ranging upto cubic yards per hour. The material is so quick setting that 12 inchknobs of material have been built up on vertical surfaces withoutsloughing. The concrete sets so quickly that even when water is flowingthrough an opening to be covered with concrete the hole can be coveredwithout the water affecting it. For example, in a tunnel through which afull flow of water was flowing, a concrete mixture was sprayed. Theconcrete completely sealed off the opening through which the water wasrunning without difficulty. The machine and method of this inventionoffer advantages over those known in the prior art in (1) higherproduction, (2) less dust, (3) less skill required by the operator ofthe nozzle as he does not have to control and observe rebound of theconcrete being applied, (4) precontrol of water content of the concretemixture, allowing optimum water content and minimum rebound, (5) nomoisture control of the sand, (6) versatility of the apparatus (that is,it can be used for pressure grouting or for various other applications)and (7) easy maintenance and easy clean-up. No build-up of material ineither the mixing equipment or the nozzle was noted during operationover fairly long periods of time. The pump and line are easily cleaned.The mixing equipment needs only to be washed out. No build-up in thelast 6 feet of delivery hose was experienced in spite of the addition ofaccelerator to the wet concrete at a point 6 feet back of the nozzle.Another advantage of the machine of this invention is the ability toturn the accelerator on and off at will while applying the concrete. Theaccelerator powder used in most applications is expensive and it ishighly desirable to be able to control the amount of accelerator used tominimize expense.

I claim:

1. Apparatus for spraying a continous stream of wet semi-fluid materialcapable of setting to a hard end product against a work surfacecomprising:

a spray nozzle,

a positive pump metering and pumping semi-fluid material to a dischargeoutlet thereof, means for suspending the semi-fluid material deliveredto the discharge outlet in a gaseous medium and delivering it from thedischarge outlet to the spray nozzle, said means including a conduitconnected between the discharge outlet of the pump and the spray nozzle,and means impinging a compressed gas at an angle to the stream ofsemi-fluid material metered from the discharge outlet into the conduitat a pressure sufficient to shear discrete pieces of the semi-fluidmaterial extruded into the gaseous stream by the pump and convey them inthe suspended gas stream to the spray nozzle. 2. Apparatus for sprayinga continuous stream of wet semi-fluid material capable of setting to ahard end product against a work surface comprising:

a spray nozzle, a rotary pump for metering the semi-fluid material to adischarge outlet, the rotary pump including a stationary ring, acompressible hose having circumferentially placed inlet and outlet portstherein extending about and bearing against the interior surface of thestationary ring, and a power driven rotor compressing the hose andproducing a fluid pocket of material moving about the circumference ofthe ring progressively from the inlet port for extrusion of thesemi-fluid material through the outlet port, and

means for suspending the semi-fluid material delivered to the dischargeport by the pump in a gaseous medium and delivering it to the spraynonle, said means including a conduit connected between the dischargeport of the pump and the spray nozzle, and means impinging a compressedgas at an angle to the stream of semi-fluid material extruded into theconduit by the pump at a pressure sufiicient to shear discrete pieces ofthe semi-fluid material and convey them suspended in the gaseous streamto the spray nozzle.

3. The apparatus'of claim 2 wherein the means for suspending thesemi-fluid material includes a T-section with the base of the T"connected to the discharge port of the pump, with the conduit connectedto one side of the top of the T", and wherein the compressed gas isdelivered through the other side of the top of the T" for impingement atsubstantially right angles to the semifluid material extruded into theT-section by. the pump at a pressure sufficient to suspend discretepieces of the semifluid material and convey them to the spray nozzlethrough the conduit.

4. Apparatus for spraying a continuous stream of a wet semi-fluidmaterial capable of setting to a hard end product against a work surfacecomprising:

a spray nozzle,

a positive pump metering and pumping the semi-fluid material to thedischarge outlet of the pump,

means for suspending the semi-fluid material delivered to the dischargeoutlet of the pump in a gaseous medium and delivering it to the sprayingnozzle, said means including a conduit connecting the discharge outletof the pump and the spray nozzle, and a means intersecting the conduitimpinging a compressed gas at an angle to the stream of semifluidmaterial extruded into the gas stream by the pump at a pressuresufficient to shear discrete pieces of the semi-fluid material andconvey them suspended in the gaseous stream to the spray nozzle,

metering means for metering a dry, particulate quickset additive for thesemi-fluid material in a predetermined weight ratio of additive tosemi-fluid material,

a second conduit connecting the discharge outlet of the metering meansintersecting the conduit carrying the stream of gas-suspended semi-fluidmaterial before ejection of the semi-fluid material from the nozzle, and

means supplying compressed gas to suspend and convey the particulateadditive into contact with the gas-suspended semi-fluid material.

5. The apparatus of claim 2 wherein the semi-fluid material is acementitious material.

6. The apparatus of claim 4 wherein the metering means includes aholding vessel for the additive, agitator means within the vessel, andfeed means in communication within the vessel for feeding predeterminedamounts of additive into the second conduit.

7. The apparatus of claim 6 wherein the pump and metering means aredirectly connected for delivery of a predetermined weight ratio ofsemi-fluid material to quick-setting additive.

1. Apparatus for spraying a continous stream of wet semi-fluid materialcapable of setting to a hard end product against a work surfacecomprising: a spray nozzle, a positive pump metering and pumpingsemi-fluid material to a discharge outlet thereof, means for suspendingthe semi-fluid material delivered to the discharge outlet in a gaseousmedium and delivering it from the discharge outlet to the spray nozzle,said means including a conduit connected between the discharge outlet ofthe pump and the spray nozzle, and means impinging a compressed gas atan angle to the stream of semi-fluid material metered from the dischargeoutlet into the conduit at a pressure sufficient to shear discretepieces of the semi-fluid material extruded into the gaseous stream bythe pump and convey them in the suspended gas stream to the spraynozzle.
 2. Apparatus for spraying a continuous Stream of wet semi-fluidmaterial capable of setting to a hard end product against a work surfacecomprising: a spray nozzle, a rotary pump for metering the semi-fluidmaterial to a discharge outlet, the rotary pump including a stationaryring, a compressible hose having circumferentially placed inlet andoutlet ports therein extending about and bearing against the interiorsurface of the stationary ring, and a power driven rotor compressing thehose and producing a fluid pocket of material moving about thecircumference of the ring progressively from the inlet port forextrusion of the semi-fluid material through the outlet port, and meansfor suspending the semi-fluid material delivered to the discharge portby the pump in a gaseous medium and delivering it to the spray nozzle,said means including a conduit connected between the discharge port ofthe pump and the spray nozzle, and means impinging a compressed gas atan angle to the stream of semi-fluid material extruded into the conduitby the pump at a pressure sufficient to shear discrete pieces of thesemi-fluid material and convey them suspended in the gaseous stream tothe spray nozzle.
 3. The apparatus of claim 2 wherein the means forsuspending the semi-fluid material includes a T-section with the base ofthe ''''T'''' connected to the discharge port of the pump, with theconduit connected to one side of the top of the ''''T'''', and whereinthe compressed gas is delivered through the other side of the top of the''''T'''' for impingement at substantially right angles to thesemi-fluid material extruded into the T-section by the pump at apressure sufficient to suspend discrete pieces of the semifluid materialand convey them to the spray nozzle through the conduit.
 4. Apparatusfor spraying a continuous stream of a wet semi-fluid material capable ofsetting to a hard end product against a work surface comprising: a spraynozzle, a positive pump metering and pumping the semi-fluid material tothe discharge outlet of the pump, means for suspending the semi-fluidmaterial delivered to the discharge outlet of the pump in a gaseousmedium and delivering it to the spraying nozzle, said means including aconduit connecting the discharge outlet of the pump and the spraynozzle, and a means intersecting the conduit impinging a compressed gasat an angle to the stream of semi-fluid material extruded into the gasstream by the pump at a pressure sufficient to shear discrete pieces ofthe semi-fluid material and convey them suspended in the gaseous streamto the spray nozzle, metering means for metering a dry, particulatequick-set additive for the semi-fluid material in a predetermined weightratio of additive to semi-fluid material, a second conduit connectingthe discharge outlet of the metering means intersecting the conduitcarrying the stream of gas-suspended semi-fluid material before ejectionof the semi-fluid material from the nozzle, and means supplyingcompressed gas to suspend and convey the particulate additive intocontact with the gas-suspended semi-fluid material.
 5. The apparatus ofclaim 2 wherein the semi-fluid material is a cementitious material. 6.The apparatus of claim 4 wherein the metering means includes a holdingvessel for the additive, agitator means within the vessel, and feedmeans in communication within the vessel for feeding predeterminedamounts of additive into the second conduit.
 7. The apparatus of claim 6wherein the pump and metering means are directly connected for deliveryof a predetermined weight ratio of semi-fluid material to quick-settingadditive.